Protein domains as units of genetic transfer

TL;DR

This study reveals that genetic transfer in prokaryotes often occurs at protein domain boundaries, indicating that protein domains serve as fundamental units of genetic exchange.

Contribution

It provides the first systematic analysis linking genetic recombination events to protein structural domains in prokaryotic genomes.

Findings

Breakpoints are closer to protein domain boundaries than expected by chance.

Recombination is more frequent among more divergent sequences.

Structural features influence the sites of genetic transfer.

Abstract

Genomes evolve as modules. In prokaryotes (and some eukaryotes), genetic material can be transferred between species and integrated into the genome via homologous or illegitimate recombination. There is little reason to imagine that the units of transfer correspond to entire genes; however, such units have not been rigorously characterized. We examined fragmentary genetic transfers in single-copy gene families from 144 prokaryotic genomes and found that breakpoints are located significantly closer to the boundaries of genomic regions that encode annotated structural domains of proteins than expected by chance, particularly when recombining sequences are more divergent. This correlation results from recombination events themselves and not from differential nucleotide substitution. We report the first systematic study relating genetic recombination to structural features at the protein level.